Differential vasoproliferative traits of <i>Bartonella henselae</i> strains associated with autotransporter BafA variants

<i>Bartonella henselae,</i> a Gram-negative facultative intracellular bacterium, is the etiological agent of cat-scratch disease and also causes bacillary angiomatosis in immunocompromised individuals. Although the ability to promote vascular endothelial cell proliferation differs among <i>Bartonella</i> species, variations among strains within <i>B. henselae</i> remain unclear. <i>Bartonella</i> angiogenic factor A (BafA) and <i>Bartonella</i> adhesin A (BadA) have been identified as autotransporters of <i>B. henselae</i> that are involved in endothelial cell proliferation. Although strain-specific differences in the expression of BadA and the VirB/D4 type IV secretion system have been reported, BafA expression among <i>B. henselae</i> strains has yet to be examined. Therefore, the present study investigated the proliferation-promoting ability of 13 <i>B. henselae</i> strains from several sources in human umbilical vein endothelial cells (HUVECs). We identified BafA variants 1 and 2 based on the deduced amino acid sequences of its passenger domain. The recombinant proteins of both variants exhibited similar proliferation activity against HUVECs. However, BafA variant 2 strains showed cytotoxicity at a high bacterial inoculum in a direct coculture with HUVECs, which was attenuated in an indirect coculture. These strains, in contrast to BafA variant 1 strains, highly expressed BadA and exhibited bacterial aggregation. Based on a core genome SNP analysis of 50 <i>B. henselae</i> strains, the BafA variant types corresponded to clades 1-4. These results indicate that vasoproliferative traits differ among <i>B. henselae</i> clades based on the variant types. Therefore, this study provides a new conceptual framework in which the clades of <i>B. henselae</i> may predict their pathogenicity in humans.IMPORTANCE<i>Bartonella</i> species including <i>Bartonella henselae</i>, <i>Bartonella quintana</i>, and <i>Bartonella bacilliformis</i> cause vasoproliferative lesions. Their proliferation-promoting ability in vascular endothelial cells differs among <i>Bartonella</i> species; however, it is unclear whether these differences exist among <i>B. henselae</i> strains. We herein showed that <i>B. henselae</i> strains exhibited variable proliferation-promoting ability and cytotoxicity in vascular endothelial cells, which corresponded to the <i>bafA</i> gene variants possessed by the strains. The expression levels of <i>Bartonella</i> angiogenic factor A (BafA) and <i>Bartonella</i> adhesin A, as well as the degree of proliferation-promoting ability and cytotoxicity in endothelial cells, varied among the strains. A core genome SNP analysis of strains using whole genome sequencing data divided <i>B. henselae</i> strains into four clades, with each clade corresponding to BafA variants 1-4. These results suggest the differential vasoproliferative potency of <i>B. henselae</i>, with potential implications in clinical management, including risk stratification and predictions of the clinical course.